In the manufacture of carpeting and other textile materials, it is conventional practice to apply thereto various chemical agents such as backsizing agents, adhesives, foam backings, and the like, and to thereafter dry and/or cure such applied chemical agents at elevated temperatures by passing the treated carpet or textile substrate through a drying oven. In such drying and/or curing operation, the treated substrate is typically supported at each longitudinal edge thereof by one of two tenter chains (or tenter cables) each of which have tenter pins affixed thereto for securing said substrate to the respective tenter chain. Such chains or cables are in turn supported and guided through the oven by tenter rails (or tenter channels) and such chains or cables are in a continuous fashion, circulated or rotated through said oven, thereby transporting the treated substrate therethrough.
The drying ovens employed in the aforementioned drying/curing operation (and the tenter chains or cables and the tenter rails or channels thereof) are typically fairly long (e.g., in the range of up to 100 or 200 feet in length or more) in order to provide sufficient residence time in the oven to adequately dry and/or cure the treated substrate as it passes therethrough. Further, the width of such ovens (and thus the maximum possible distance between the supporting tenters) is also typically substantial (e.g., on the order of 15 feet or more) in order to accommodate the largest carpeting or textile material widths currently in common usage. Moreover, the drive means (e.g., sprockets, pulleys, etc.) for the tenter chain (or tenter cables) and the tenter rails (or channels) therefor are typically adjustable (a) in order that the distance between such rails or channels (and between the tenter chains or cables supported thereby) can be adapted to accommodate carpeting or textiles of various widths and (b) in order that individual sections of each of the tenter rails can be aligned in a fashion such that the tenter chains supported thereby form 2 generally straight and generally parallel lines throughout the length of the oven (i.e., such that the distance between each set of such tenter rail or channel sections is substantially the same along the length of said oven).
Often during use of the above-described drying ovens, the supporting tenter rails or channels, and thus the tenter chains or cables supported thereby, can become misaligned (e.g., one or more sets of the tenter rail sections can be initially misadjusted or can become misaligned through normal wear, breakage, etc., such that the distance therebetween is not substantially the same along the entire length of the drying oven) with the result that the tenter chains or cables do not maintain the desired generally parallel relationship relative to each other as they traverse the length of said oven. Such misalignment can be very troublesome and costly in that it can cause product defects such as loose backing in carpeting (commonly referred to as "loose jute"), etc., and can thereby lead to substandard or defective material requiring special treatment for repair or salvaging thereof or perhaps being incapable of being salvaged at all. Moreover, when such product defects are detected, it often becomes necessary to shut down production and to check the tenter rail or channel alignment to determine if misalignment is the cause thereof.
In checking for the aforementioned problem of tenter misalignment, it has generally been the practice of the industry (a) to shut down production, (b) to remove the treated substrate from the oven, (c) to permit the oven to cool down to approximately ambient temperature, (d) to manually measure the distance between the tenter chains (or cables) at the numerous sets of supporting tenter rail or channel sections along the oven length, (e) to make adjustments necessary to properly align any set of such rail sections found to be out of alignment and (f) finally, to reheat the oven to operating temperature and thereafter to restart production. In addition, in step (d), above, it is also generally necessary to attach a tensioning device across the individual sets of tenter rail sections during the measurement thereof to simulate the weight of the treated substrate thereon since often times a misalignment problem may be apparent (and thus detectable) only under such circumstances.
Naturally, the aforementioned method of checking tenter alignment has several serious drawbacks not the least of which include the substantial unproductive "down time" and energy resource wastage involved in cooling and reheating such a typically massive drying oven as well as the substantial "down time" involved in manually applying tension to, and measuring the width of, each of the numerous sets of tenter rail or channel sections in such an oven. Accordingly, it is highly desirable to provide a means by which the aforementioned measurement can be quickly and accurately accomplished without the above-described disadvantages which are attendant to the above-noted manual methods.